MaterialApp using in runApp

  MaterialApp with Stateless Widget

import 'package:flutter/material.dart';

void main(){
   runApp(MaterialApp(
  debugShowCheckedModeBanner: false,
  initialRoute: '/',
  routes: {
    '/':(context)=> MyApp(),
  },
));     💪 // MaterialApp
}

class MyApp extends StatelessWidget {
  const MyApp({Key? key}) : super(key: key);

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text("Firebase Messaging"),
        flexibleSpace: Container(
          decoration: BoxDecoration(
            gradient: LinearGradient(
              colors: [Colors.green,Colors.lightGreenAccent],
              begin: Alignment.bottomRight,
              end: Alignment.topLeft,
            ),
          ),
        ),
      ),
      body: SafeArea(
        child: Container(
          child: ListView(
            children: [
              Container(
                padding: EdgeInsets.symmetric(vertical: 10,horizontal: 10),
                margin: EdgeInsets.all(10.0),
                width: 100,
                height: 200,
                color: Colors.blue,
                child: Text("Raj"),
              ),
            ],
          ),
        ),
      ),
    );     💪 // Scaffold
  }
}